According to a report, 84% of New York City fast food workers claimed to be victims of wage theft. Photograph: Graeme Robertson

New York's attorney general on Thursday said he is investigating the fast food industry in the state after allegations of massive wage theft by employers affecting some of the lowest paid workers in America.

The revelation also comes after a series of strikes and walk-outs by fast food workers in New York City as well as Detroit, Chicago, St Louis and Milwaukee in recent weeks. The protests have been aimed at highlighting low wages and anti-union intimidation.

A report, conducted by research firm Anzalone over the last three months, found that some 84% of New York City fast food workers claimed to have been victims of some form of wage theft.

Damien LaVera, a spokesman for New York state attorney general Eric Schneiderman, said the report's findings were "deeply troubling" news. "We take the allegations seriously, which is why our office is investigating fast food franchisees. New Yorkers expect companies doing business in our state to follow laws set up to protect working families," he added.

The report found commonplace incidents such as not being paid overtime, being asked to perform tasks without being paid, not being reimbursed properly for expenses such as uniforms and being forced to pay for meals they have not eaten. Some 30% of employees reported getting their pay checks late or even having them bounce.

"There is a widespread crime wave in the fast food industry. The epidemic is preying on the city's most vulnerable residents – the men and women who make $7.25 an hour and are the least able to afford it," said Jonathan Westin, campaign director of Fast Food Forward, the group that is helping organise the protest movement.

A source with knowledge of the extent of the investigation told the Guardian that Schneiderman had already issued several subpoenas to one unnamed major parent company in the fast food sector and was also investigating franchisees running restaurants in the rest of New York state.

The news comes as American labor groups are putting an increasing stress on trying to organise low-wage workers in the fast food industry and among major retail chains like Walmart. In part this is because of the low wages and poor conditions so often prevalent at the bottom end of the US economy, but it is also because America's tepid recovery from the Great Recession has seen a boom in low wage jobs. Aside from the fast food industry, strikes and walkouts have also hit Walmart stores and much of its outsourced supply chain over the past year.

The campaigns have won the support of traditional civil rights groups, like the National Association for the Advancement of Colored People. "We can't allow such flagrant violations of the law. It's time for the fast food industry to come clean, and do the right thing. They need to change their ways. And they need to start paying the 50,000 men and women they employ in our city enough to support their families," said Hazel Dukes, president of the the NAACP New York State Conference.

• This headline was amended on 17 May to clarify that it is the fast food employers who are accused of wage theft.